Consumer products can provide a hospitable environment for rapid microbial growth. Such exposure can, and frequently does, result from inadvertent microbial inoculation of the product during manufacturing or packaging. Spoilage microorganisms, for example in food products, can then rapidly proliferate by feeding on nutrients provided by the product.
Preservatives, such as sorbates, benzoates, organic acids, and combinations thereof have been used in various products, particularly foods and beverages, to provide some degree of microbial inhibition. However at levels effective to inhibit microbial growth, some of these preservatives can contribute off-flavors in the product, thus making the product undesirable for its intended purpose. Similarly, natural preservatives, such as natamycin, are frequently used in food and beverage products to inhibit microbial growth. Unfortunately, while these natural preservatives may be effective against either yeast or bacteria, they may not be effective against both.
It has been disclosed that the essential oil of mustard plants, which contain isothiocyanates, exhibits an antibacterial and antimycotic effect in oral therapies and on certain foods. See e.g., Sekiyama et al., U.S. Pat. No. 5,334,373, assigned to Nippon Sanso Corp., issued Aug. 2, 1994; and Madaus et al., U.S. Pat. No. 3,998,964, issued Dec. 21, 1976. The isothiocyanate compounds in mustard essential oils are the active agents that provide the antimicrobial effect. The essential oil derived from white or yellow mustard plants (Sinapis alba or Brassica alba), also provides the foregoing antibacterial and antimycotic benefits, however, it is known in the art that white mustard essential oil is a viscous oil that is, therefore, difficult to evenly disperse within solid food products or on solid food product surfaces. Furthermore, isothiocyanate compounds are effective antimicrobial agents at relatively low usage levels. Therefore, it can be difficult to uniformly distribute such low levels within a solid food matrix or on the surface of a solid food product. Moreover, the principal isothiocyanate present in the white mustard essential oil, 4-hydroxybenzyl isothiocyanate, is a moisture-sensitive compound that begins to degrade (i.e. hydrolyze) within hours of being exposed to moisture. When degraded, the 4-hydroxybenzyl isothiocyanate forms, among other compounds, 4-hydroxybenzyl alcohol.
Currently, the mustard processing industry makes use of the white mustard flour primarily, while the essential oil is largely ignored. In fact, to make use of the white mustard flour without the ‘heating’ sensation of mustard, the ground mustard flour is subjected to a thermal deactivation step. Here the enzyme myrosinase, which catalyzes the formation of 4-hydroxybenzyl isothiocyanate from its precursor 4-hydroxybenzylglucosinolate, is intentionally deactivated so that the essential oil does not form when the flour is mixed with moist food products such as meat and sausage. Additionally, because of its instability, 4-hydroxybenzyl isothiocyanate is not currently available commercially, whether as a natural product or as a pure chemical.
Accordingly, for all of the above reasons, white mustard essential oil has not been widely known or widely utilized in the art for its antibacterial and antimycotic effect. This is particularly true for solid food products, for which uniform dispersion of the white mustard essential oil may be difficult and for which prolonged periods of storage may be required, hence, prolonged periods of exposure to moisture.
However, the present inventors have surprisingly discovered that by generating the white mustard essential oil by adding water to ground mustard, extracting the white mustard essential oil using solvents or supercritical fluids, rapidly drying the essential oil by removing residual moisture, and then intimately blending the resulting white mustard essential oil with a hygroscopic carrier, the moisture-sensitive isothiocyanate compounds contained therein are stabilized. Hence, the blend of white mustard essential oil with a hygroscopic carrier is, thereafter, capable of being used as an effective antibacterial and antimycotic agent for solid food products.